It's "A" because Xenon has 54 protons and 78 neutrons.
It's"B" because the number of protons in an atom is the same as the number of electrons in an atom. They have the same number unless there is a charge on it that either adds up or subtracts it.
<em><u>Unit conversion is very important because the rest of the world other than three contries uses the metric system. So, converting unitsis important in science because it uses the metric system. The metric system aremeasurements like cm, m, l, mL, etc.</u></em>
